Large Redshifts in Emission and Excitation from Eu<sup>2+</sup>-Activated Sr<sub>2</sub>SiO<sub>4</sub> and Ba<sub>2</sub>SiO<sub>4</sub> Phosphors Induced by Controlling Eu<sup>2+</sup> Occupancy on the Basis on Crystal-Site Engineering

Abstract

The photoluminescence properties of Eu2+-activated α’-Sr2SiO4 and α’-Ba2SiO4 with a high Eu2+ concentration were investigated. In the case of Sr2-xEuxSiO4, emission was shifted from 585 to 611 nm with increasing the total Eu2+ concentration (x) from 0.1 to 0.8. This trend was similar to that in Ba2-xEuxSiO4, where the emission was shifted from 513 to 545 nm. The large redshifts in both the excitation and emission spectra were discussed in terms of the Eu2+ occupancies on two kinds of M sites and their local structural changes (M: Sr and Ba).